Fourier transform infrared (FTIR) spectrometers are utilized to perform accurate and efficient identification of the chemical composition of a sample. Such spectrometers typically incorporate a Michelson interferometer having a moving mirror. The interferometer modulates the infrared beam from an infrared source to provide an output beam in which the intensity of the infrared radiation at various wavelengths is periodically varied. The output beam is focused and passed through or reflected from a sample, after which the beam is collected and focused onto a detector. The detector provides a time varying output signal which contains information concerning the wavelengths of infrared absorbance or reflectance of the sample. Fourier analysis is then performed on the output signal data to yield usable information on the chemical composition of the sample.
Conventional FTIR spectrometers include a sample chamber in which a sample is held in a position to be exposed to the infrared beam from the spectrometer. The sample which is to be analyzed may take various physical states, i.e., a liquid, solid or gas, and solid samples may have various physical characteristics. For example, a solid material to be analyzed may be in the form of a block or sheet of material (e.g., polymer plastics), in the form of powders or granulates, or in specific formed shapes (e.g., pharmaceutical pills and capsules). An example of a infrared spectrometer system that can be utilized to carry out analysis of pharmaceutical samples in both the reflectance mode and the transmission mode is shown in U.S. Pat. No. 6,667,808, entitled Multifunctional Fourier Transform Infrared Spectrometer System.
Pharmaceutical tablets may take various shapes and sizes. Typically, an operator will test one tablet at a time by placing the tablet in a sample position where it is usually engaged with a holder or variable aperture which locates the tablet in the proper sample position and which also minimizes the infrared light transmitted around the tablet. Where a large number of tablets are to be sampled, a significant amount of operator time is required to remove each tablet and replace it with another tablet in the proper position for sampling, and to attend to the spectrometer while the analysis is carried out. Tablet holding wheels or turntables have been used to allow several tablets to be deposited by the operator at one time on the wheel, which is then automatically advanced to bring one of the tablets at a time into the sample position for analysis. However, when sampling of one batch of tablets of a particular size and shape is completed, and sampling of a new batch of tablets of a different size and shape is to be carried out, a new specialized holder is generally required to accommodate the size and shape of the new batch of tablets to be analyzed.